1. Field of the Invention
This invention relates to a vehicle navigation system for aurally directing the movement of a vehicle so that it will reach its intended destination.
2. Description of the Related Art
Various kinds of apparatuses have been developed for use on vehicles in an effort to reduce the driver's burden; among such conventional apparatuses, there is a navigation system for directing the movement of a vehicle so that it will reach its intended destination. The conventional navigation system is equipped with the function of showing the driver a route to be selected when the vehicle passes a turning point such as a crossing and the function of directing the route aurally. This conventional navigation system is exemplified by Japanese Patent Laid-Open Publication No. HEI 1-173819.
With the conventional navigation system using aural guidance, notice as to whether a vehicle should turn to the right or left is automatically given to the driver aurally when the vehicle arrives at a crossing, as the current position of the running vehicle is detected at all times. For instance, aural guidance such as "turn to the left at the crossing 100 m ahead" is given when the vehicle arrives at a position 100 m short of the crossing.
Therefore, even in the absence of local map knowledge, the driver can take a correct driving route, without watching the display of the system.
Assuming that the vehicle is traveling on a road the driver knows somewhat, an aural notice would not be necessary. Instead, the route will have been searched as a matter of precaution. Any display on the screen will not disturb the driver if he/she does not look at the screen, but an aural notice will reach the driver's ears whether they like it or not. As a hypothetical solution, such an aural notice could be cut off by means of a switch so that no announcement disturbs the driver.
If route searching is being made when traveling, it may be that the driver requires some help with the navigation. Practically speaking, route guidance on the display screen is more difficult to follow, as compared to aural route guidance. It is therefore preferable that the driver enjoy aural route guidance only at the driver's request.